Clamping force applying means for molding machines

ABSTRACT

A molding machine comprising a plurality of clamping force applying means, each of which includes a plurality of interconnected pistons fluid actuatable for conjointly applying clamping force. Bypass means are provided for causing the actuating fluid to be bypassed around pistons of each of the clamping force applying means in the event of piston overtravel during the piston movement to apply clamping force.

I United States Patent 1191 1111 3,847,528 Farrell Nov. 12, 1974 [54] CLAMPING FORCE APPLYING MEANS 2,556,979 6/1951 Purcell 91/437 x FOR MOLDING MACHINES 3,015,849 1/l962 Mittelstadt.... 425/DIG. 223 3,465,387 9/1969 Allard et al... 435/149 lnvemorl Robert Farrell, Nashua, 3.656877 4 1972 Aoki 425/242 x [73] Assignee: Improved Machinery Inc., Nashua,

NH, Primary ExaminerJ. Spencer Overholscr Assistant Examiner-David S. Safran [22] Flled: 1972 Attorney, Agent, or Firm-Robert R. Paguin [21] Appl. No.; 310,255

[57] ABSTRACT h r -:---,-:--::;-'uf iggg lg g A molding machine comprising a plurality of clamping [51] Int Cl 1 i force applying means, each ofwhich includes a plurality of interconnected pistons fluid actuatablc for con- [58] Field of z g bf g g jointly applying clamping force. Bypass means are prov vided for causing the actuating fluid to be bypassed around pistons of each of the clamping force applying [56] References Cited means in the event of piston ovcrtravel during the pis- UNITED STATES PATENTS ton movement to apply clamping forcc. 1,612,779 12 1926 Mercer 1. 92/151 X 2C 3D F aims, rawmg lgures 74 58 76 74 48 76 74 p1 J a 1? 1'1 L: I 1 1 7 J 1 F 78 78 L A g I h \I Y I l I E 70 86 54 4 84 7238 66 72 7 I I I I I I I I g 86 82 6O 80 so so 68 60 so so CLAMPING FORCE APPLYING MEANS FOR MOLDING MACHINES The present invention relates generally to molding machines and more particularly to means for applying clamping force during the operation of a molding machine.

Conventionally, as described in US. Pat. No. 3,465,387, issued Sept. 9, 1969 and assigned to the assignee of the present invention, clamping force is frequently applied in a molding machine by. relatively large diameter pistons or load cells. However, such conventional clamping force applying pistons or load cells must be substantially redesigned for each size of molding machine and, due to their large diameter, are difficult to manufacture and undesirably heavy in weight.

An object of the present invention is to provide a new and improved clamping force applying means for molding machines, which clamping force applying means is particularly constructed and arranged to permit the application of high clamping force without the necessity for a large diameter piston or load cell.

Another object of the invention is to provide a new and improved clamping force applying means for molding machines, which clamping force applying means is particularly constructed and arranged to provide a relatively large clamping force for a given piston diameter.

Another object is to provide a new and improved clamping force applying means which is particularly constructed and arranged to permit its use in machines of different sizes without substantial redesign of the clamping force applying means.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein, as will be understood, the preferred form of. the invention has been given by way of illustration only.

In accordance with the invention, a molding machine may comprise a first platen, a second platen moveable towards-and-away from the first platen, at least one clamping force transmitting means for transmitting clamping force to a mold between the platens, and clamping force applying means for applying clamping force through such transmitting means, the clamping force applying means comprising for each such transmitting means a plurality of pistons actuatable for conjointly applying clamping force through the transmitting means, and means for causing the pistons to be actuated to apply the clamping force.

Referring to the drawings:

FIG. 1 is an elevational view, partially broken away and in section, of an injection molding machine including a plurality of clamping force applying means constructed in accordance with one embodiment of the invention;

FIG. 2 is an enlarged, elevational sectional view illustrating one of the clamping force applying means of the molding machine shown in FIG. 1, in unpressurized condition;

FIG. 3 is a view generally similar to FIG. 2, but showing such clamping force applying means during its application of clamping force.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, FIG. 1 illustrates a plurality of clamping force applying means constructed in accordance with one embodiment of the invention as applied to a molding machine of the type described in US. Pat. No. 3,590,418, issued July 6, 1971 and assigned to the assignee of the present invention. It will be understood, however, that the present invention has been shown and described as applied to such a machine only for the purposes of illustration; and the invention is equally applicable to many other forms of molding machines.

The molding machine illustrated in FIG. 1 comprises a generally vertical first platen 10 mounted uponthe upper surface of a ground supported base or base pad 12 which also carries the injection unit of the molding machine, such injection unit being designated generally as 14. The injection unit 14 may be of any suitable conventional construction and, as shown, includes a receiving hopper 16, an injection ram device 18, a plasticizing and feed device 20, and a discharge nozzle 22 which projects through an opening through the first platen 10. A generally vertical second platen 24, oppositely disposed to the first platen 10, is suspended by a supporting shoe 26 from a generally horizontal guide track 28 which is, in turn, ground mounted by a plurality of supporting posts 30. The platens 10,24 carry the usual mating mold sections or halves 32,34; and the second platen 24 is, during the operation of the machine, driven by a cylinder-and-piston actuator 36 towards-and-away from the first platen 10 between a mold closed position (shown in solid lines in FIG. 1)

and a mold fully open position (shown in broken lines in FIG. 1).

The second platen 24 carries four tie rods 38 which project generally horizontally from the second platen 24 towards the first platen 10 and, with the second platen 24 in its mold closed position, slidably extend through openings in the first platen 10 into individual breech machanisms, each designated generally as 40, associated with the latter. The tie rods 38, as illustrated, extend through the second platen 24 into individual retraction tubes 42 mounted on the second platen 24 and may be in the manner described in US. Pat. No. 3,465,387, issued Sept. 9, 1969 and assigned to the assignee of the present invention, adjustable by drive means (not shown) on the second platen'24 to vary the portions of their lengths projecting from the second platen 24 towards the first platen 10. Such portions of the lengths of the tie rods 38, as will be understood, are preferably maintained sufficiently short to permit the tie rods 38 to be entirely removed from their openings in the first platen 10 during the movement of the second platen 24 away from the latter, thereby facilitating the discharge of a formed part from between the mold halves 32,34.

The molding machine, moveover, includes the usual individual breech mechanisms for the tie rods 38, such breech mechanisms each being designated generally as 40 and in the normal manner each including a plurality of breech blocks 44,46 relatively driven towards-andaway from each other by driving means (not shown) to,

respectively, grip and release a therebetween tie rod v38. The breech mechanisms 40, per se, may be of any Further details of the construction and operation of a molding machine of the general type illustrated, if desired, can be obtained from the beforementioned US. Pat. No. 3,590,418; and it will be understood that, as disclosed in such patent, the tie rods 38 alternatively could be mounted to the first platen 10' in which event the breech mechanisms 40 and hereinafter described clamping force applying means would be associated with the second platen 24 for movement therewith.

Each breech mechanism 40 is provided with an individual clamping force applying means adapted to apply clamping force to the mold sections 32,34 through a clamping force transmitting means including the breech blocks 44,46 of the breech mechanism 40, the tie rod 38 gripped thereby, and the second platen 24. All of the clamping force applying means of the molding machine are of identical construction and arrangement; and hence, although only one thereof has been illustrated in detail in FIGS. 2 and 3, it will be understood that the others are also of the illustrated construction and arrangement.

More particularly, as shown in FIGS. 2 and 3, each clamping force applying means comprises an elongated, annular, openended, stationary housing or sleeve 48 which is longitudinally interposed intermediate the first platen l and a respective pair of cooperative breech blocks 44,46 coaxial with a tie rod 38 to include an end 50 adjacent to the first platen l0 and an end 52 adjacent to the breech blocks 44,46. Each housing 48 may be at its end 50 affixed to the first platen l0 and at such end 50 includes an integral, annular, end wall 54 projecting inwardly into the interior of the housing 48. Each housing 48 includes a plurality of integral, annular divider walls 56 which project inwardly into the interior of the housing 48 at spaced locations throughout its length and, together with portions 58 of the housing 48 and the housing end wall 54, define within the housing 48 a plurality of aligned, annular cylinders 60 which are coaxial with the respective tie rod 38. As illustrated, the cylinder 60 most adjacent to the housing end 52, and hence most adjacent to the breech blocks 44,46, is open to the breech blocks 44,46 whereby the latter partially close an end of such cylinder 60. The cylinders 60 within each housing 48 are shown as being four in number; however, it will be understood that such number has been shown for the purposes of illustration only and the number of cylinders 60 and hereinafter described contained pistons, provided in any embodiment of the invention is dependent upon the amount of clamping force desired or required and the diameter of cylinders 60 and pistons to be used. Hence, the number of employed cylinders 60 and contained pistons could in some embodiments of the invention be greater than four in number while in other embodiments being as few as two or three.

Each clamping force applying means, as shown in FIGS. 2 and 3, includes four, aligned, annular pistons 62, each slidably disposed in one of the cylinders 60 for movement longitudinally of the housing 48; and the piston 62 in the open-ended cylinder 60 at the housing end 52 is directly engagable with the breech blocks 44,46 to apply clamping force through the latter to a tie rod 38 gripped therebetween. The pistons 62, as illustrated, are each formed integral with an annular sleeve 64 which projects from the piston 62 towards the first platen and the pistons 62 are interconnected by bolts 66 into a unitary, annular, openended piston as sembly, designated generally as 68, wherein the pistons 62 are coaxially arranged longitudinally spaced apart by the sleeves 64 and the latter close the inner peripheries of the cylinders 60. The piston assembly 68 is, of course, coaxial with the surrounding housing 48; and the elongated opening 70 through each piston assembly 68 is dimensioned to permit the corresponding tie rod 38 to be axially moved into and out-of the assembly 68.

Pressure fluid for axially moving the piston assembly 68 to apply clamping force (that is, for moving the piston assembly 68 to the right, as viewed in FIGS. 2 and 3) is supplied to each cylinder 60 thereof through a bore 72 in the housing 48 and a supply conduit 74 communicating the bore 72 with a source (not shown) of the pressure fluid. Pressure fluid for axially moving the piston assembly 68 from applying clamping force (that is, for moving the piston assembly 68 to the left, as viewed in FIGS. 2 and 3) is supplied to all but the openend cylinder 60 through a bore 76 in the housing 48 and a supply conduit 78 communicating the bore 76 with a source (not shown) of the pressure fluid. Each cylinder 68, except the open-ended cylinder 60, is provided with at least one by-pass passage 80 which is formed in the wall 56 of the cylinder 60 to bypass pressure fluid around the contained piston 62 after a predetermined movement of the piston 62 during the actuation of the piston assembly 68 to apply clamping force, thereby providing overtravel protection for the piston assembly 68 to limit the build-up of pressure in the cylinder 62 and restrain piston travel. The bypass passages 80 are arranged by bypass fluid around the pistons 62 only in the event of piston overtravel and, as shown in FIG. 3, do not bypass fluid around the pistons 62 during the normal application of clamping force by the piston assembly 68. Also, the pistons 62, divider walls 56 and housing end wall 54 are provided with annular sealing rings 82,84, and 86, respectively; and annular sealing rings 88 are provided at the junctures of the sleeves 64 with the next adjacent piston 62.

The operation of the beforedescribed molding ma-. chine is believed to be apparent from the preceeding description. However, in order to insure clear understanding of the clamping force supply means of the in vention, a brief description of the previously described embodiment thereof is hereinafter given.

During the driven movement of the second platen 24 towards its mold closed position, the tie rods 38 are moved axially through the openings 70 to locate their ends intermediate the open breech blocks 44,46 of their respective breech mechanisms 40. Each tie rod during its said movement trips the usual limit switch (not shown) whereupon, after all such limit switches have been so tripped indicating that all of the tie rod ends are in position for gripping by their respective breech blocks 44,46, the latter are driven into gripping relationship with their respective tie rod ends.

After all of the tie rod ends have been so gripped and while pressure fluid is simultaneously exhausted through the bores 76 and conduits 78, pressure fluid is supplied through the supply conduits 74 and bores 72 to cause the pistons 62 to move the breech blocks 44,46 to their FIG. 3 positions, whereby the pistons 62 conjointly act through the breech blocks 44,46, the tie rods 48 and the second platen 24 to exert clamping force on the mold sections 32,34. As will be seen, the magnitude of the clamping force exerted by the interacting pistons 62, being equal to the total of the pres sure of the pressure fluid in each cylinder 60 times the annular area of the pistons 62 on which the pressure fluid acts, is substantially greater for a given piston diameter than it would be in the event that only a single piston were employed; and in the event that, during the application of the clamping force, the pistons 62 move a distance sufficient to enable the bypass passages 80 to communicate the portions of the cylinders 60 on opposite sides thereof, piston travel is thereafter limited by the bypassed fluid and further pressure build-up in the cylinders 60 is prevented. After the clamping force has been applied for the desired predetermined time period, pressurized fluid is thereafter supplied to the cylinders 60 through the conduits 78 and bores 76, while being exhausted from the open sides of the pistons 62 through the bores 72 and supply conduits 74; and the parts are thereby returned to the relative positions shown in FIG. 2.

From the preceeding description it will be seen that the clamping force applying means provided by the present invention, due to its employment of a plurality of pistons, permits the application of high clamping force without the necessity for a large diameter piston or load cell and enables the application of a relatively large clamping force for a given piston diameter. Also, it will be seen that, by variance of the number of cylinders and pistons employed, the clamping force applying means may be readily and simply varied to provide substantially any desired clamping force, thereby permitting its use in machines of different sizes without the necessity for substantial redesign of the clamping force applying means.

It will be understood, however, that, although only a single embodiment of the invention has been illustrated and hereinbefore specifically described, the invention is not limited merely to this illustrated and described single embodiment, but rather contemplates other embodiments and variations within the scope of the following claims. For example, and not by way of platens and longitudinally projecting from said one platen towards the other thereof, gripping means operatively associated with said other platen for gripping said tie rods, said gripping means for each said tie rod comprising a plurality of breech blocks located on the opposite side of said other platen from said one platen and relatively movable for gripping a therebetween said tie rod, and individual clamping force applying means operatively associated with each said tie rod for applying clamping force to a mold between said platens through the tie rod and its respective said breech blocks, each said clamping force applying means comprising means defining a plurality of cylinders aligned with its respective tie rod and on such opposite side of said other platen intermediate said other platen and the respective said breech blocks for the tie rod, the end said cylinder most adjacent to such breech blocks having its end most adjacent to the latter open thereto, a piston in each of said cylinders, said pistons being interconnected to be fluid actuatable towards-and-away from such breech blocks for conjointly applying said clamping force, said pistons being annular and containing openings aligned with the tie rod and dimensioned to permit axial movement of the tie rod through said pistons, the piston in said end cylinder being adapted to apply clamping force through said cylinder open end to such breech blocks upon fluid driving of said piston towards the latter, means for supplying pressure fluid to said cylinders for driving said pistons towards-andaway from such breech blocks, and each said clamping force applying means further comprising by-pass means for by-passing pressure fluid around all of its said pistons, except its said piston in said end cylinder, after a predetermined movement of the pistons for application of clamping force, such by-pass means comprising internal grooves in the walls defining said cylinders constructed to communicate portions of said cylinders on opposite sides of their contained pistons, said grooves being located to prevent fluid flow therethrough during the normal application of clamping force by the pistons and said grooves being at the ends of said cylinders most adjacent to said breech blocks.

2. A molding machine accordingto claim 1, wherein each said clamping force applying means further comprises annular sealing means circumferentially carried by each of its said pistons, annular sealing means intermediate its said cylinders, and annular sealing means intermediate its end said cylinder most adjacent to said other platen and the latter. 

1. In a molding machine, a first platen, a second platen movable towards-and-away from said first platen, a plurality of tie rods associated with one of said platens and longitudinally projecting from said one platen towards the other thereof, gripping means operatively associated with said other platen for gripping said tie rods, said gripping means for each said tie rod comprising a plurality of breech blocks located on the opposite side of said other platen from said one platen and relatively movable for gripping a therebetween said tie rod, and individual clamping force applying means operatively associated with each said tie rod for applying clamping force to a mold between said platens through the tie rod and its respective said breech blocks, each said clamping force applying means comprising means defining a plurality of cylinders aligned with its respective tie rod and on such opposite side of said other platen intermediate said other platen and the respective said breech blocks for the tie rod, the end said cylinder most adjacent to such breech blocks having its end most adjacent to the latter open thereto, a piston in each of said cylinders, said pistons being interconnected to be fluid actuatable towards-and-away from such breech blocks for conjointly applying said clamping force, said pistons being annular and containing openings aligned with the tie rod and dimensioned to permit axial movement of the tie rod through said pistons, the piston in said end cylinder being adapted to apply clamping force through said cylinder open end to such breech blocks upon fluid driving of said piston towards the latter, means for supplying pressure fluid to said cylinders for driving said pistons towards-and-away from such breech blocks, and each said clamping force applying means further comprising by-pass means for by-passing pressure fluid around all of its said pistons, except its said piston in said end cylinder, after a predetermined movement of the pistons for application of clamping force, such by-pass means comprising internal grooves in the walls defining said cylinders constructed to communicate portions of said cylinders on opposite sides of their contained pistons, said grooves being located to prevent fluid flow therethrough during the normal application of clamping force by the pistons and said grooves being at the ends of said cylinders most adjacent to said breech blocks.
 2. A molding machine according to claim 1, wherein each said clamping force applying means further comprises annular sealing means circumferentially carried by each of its said pistons, annular sealing means intermediate its said cylinders, and annular sealing means intermediate its end said cylinder most adjacent to said other platen and the latter. 